Math Problem Statement

Suppose X is a random variable uniformly distributed on [7,16]. Determine the standard deviation of X.

Solution

Given that XX is a random variable uniformly distributed on the interval [7,16][7, 16], the probability density function (PDF) for a uniform distribution on [a,b][a, b] is:

f(x)=1ba,foraxbf(x) = \frac{1}{b - a}, \quad \text{for} \quad a \leq x \leq b

For the interval [7,16][7, 16], we have a=7a = 7 and b=16b = 16.

Steps to find the standard deviation:

  1. Mean (Expected Value): The mean μ\mu of a uniform distribution on [a,b][a, b] is given by: μ=a+b2\mu = \frac{a + b}{2} Substituting a=7a = 7 and b=16b = 16: μ=7+162=232=11.5\mu = \frac{7 + 16}{2} = \frac{23}{2} = 11.5

  2. Variance: The variance σ2\sigma^2 for a uniform distribution on [a,b][a, b] is given by: σ2=(ba)212\sigma^2 = \frac{(b - a)^2}{12} Substituting a=7a = 7 and b=16b = 16: σ2=(167)212=9212=8112=6.75\sigma^2 = \frac{(16 - 7)^2}{12} = \frac{9^2}{12} = \frac{81}{12} = 6.75

  3. Standard Deviation: The standard deviation σ\sigma is the square root of the variance: σ=6.752.598\sigma = \sqrt{6.75} \approx 2.598

Thus, the standard deviation of XX is approximately 2.5982.598.

Would you like more details or have any questions?

Related Questions:

  1. How do you find the variance of other continuous distributions?
  2. What is the difference between standard deviation and variance?
  3. How do you calculate the expected value of any random variable?
  4. What is the significance of the uniform distribution in probability theory?
  5. How does changing the interval [a,b][a, b] affect the standard deviation?

Tip: For uniform distributions, the variance and standard deviation only depend on the length of the interval!

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Math Problem Analysis

Mathematical Concepts

Probability
Uniform Distribution
Statistics

Formulas

Mean (Expected Value) of Uniform Distribution: μ = (a + b) / 2
Variance of Uniform Distribution: σ² = (b - a)² / 12
Standard Deviation: σ = √σ²

Theorems

Uniform Distribution Theorem

Suitable Grade Level

Grades 11-12